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Penetrating keratoplasty (PKP) has been applied in corneal diseases like bullous keratopathy and Fuchs Endothelial Dystrophy since 1905. In recent years, new surgical techniques such as endothelial keratoplasty (EK) have been developed. This is how transplantations with preservation of the anterior corneal layers have become possible. Thus, the visual results have improved and shortened the visual recovery times for patients. The natural anatomy of the organ is preserved, and it is more resistant to mechanical trauma. Meanwhile, the EK has become the treatment of choice for endothelial diseases. Various methods of preparation of the donor cornea for the EK exist. In this research project two different preparation methods are investigated: The femtosecond laser assisted and the microkeratome assisted intrastromal tissue separation. It is assumed that irregularities of the posterior corneal surface contribute to the poorer visual acuity postoperatively when using femtosecond laser for preparation.
To elucidate this question in our clinical retrospective study, the morphology of the postoperative posterior corneal surface and the best corrected visual acuity of 22 patients after a DSAEK were correlated.
Eight out of 22 donor corneas were prepared with the 200 kHz VisuMax femtosecond laser (Carl Zeiss Meditec AG, Jena, Germany; femtosecond laser group), while 14 grafts were processed with the Amadeus II microkeratome (Ziemer Olphthalmic System AG, Port, Switzerland; microkeratome group). The postoperative best corrected visual acuity showed a significant difference (p = 0.038) between the two groups. The mean best corrected visual acuity in the femtosecond laser group showed a worse mean 0.48 [0.2; 0.9] logMAR than the mean of 0.33 [0.1;0.5] logMAR in the microkeratome group.
To evaluate the irregularity of the corneal endothelial morphology (RTVue; Optovue, Fremont, USA), a regression analysis (SPSS, IBM, Chicago, USA) with an ideal polynomial curve of second degree were performed to determine the root mean square error as a measure for the irregularity of the surface.
The irregularity root mean square error of 9.9 [2.2] m in the femtosecond laser group and 5.7 [2.2] µm in the microkeratome group resulted in a significant difference (p <0.001.)
A correlation between the best corrected visual acuity and the irregularity of the posterior corneal surface was confirmed with Pearson's correlation value of 0.438 (p <0.05.)
Thus our results indicate that the microkeratome assisted DSAEK graft preparation leads to lower gathers in the inner surface of the cornea, and consequently leads to superior visual acuity than the femtosecond laser method.